I had done the same offer twice, not credited

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Couple days ago, I had an offer in gptreasure, it was not be able to tracked on its system. So, I re - do it again with different email address. Today, it turn out to be the same result. What went wrong here? Sometimes, people advise me to use different email address on some offers. But it still don't work for other offers. What are tricks here? Please advise me more on this matter.